PTO wise the only thing I have is a 5' bush hog to cut 10 acres of pasture with. Mostly would be loader work and dragging a chain harrow. I can get a dk40se from him without 4-in1 bucket for $200 more than the ck. Same features...hydro drive, etc...
Was craigslist searching and ran across a Kubota L3830 hst with loader and 4-in-1 with 453 hours for $16000. Very tempted to go look at that.
As for the Deere....I looked at those and would be considering the 3320 or 3520...but the price of the 3320 he quoted me was $28955. I can only imagine what the 3720 is.
I had a CK30 (same as the CK35, couple hp less) and I now have a DK45 (same as the DK40, just a couple hp more). Either will easily handle a 5' bush hog, it would be undersized for the DK40. I've never used a 4 in 1 bucket, so I don't know what you'd be giving up, but I do know what you'd get by moving to a DK over a CK, and it's worth wayyyyyyy more than $200.
The FEL will lift 2.5X more and uses a bigger bucket. I found the FEL a little underpowered on the CK30, it's a monster on the DK45.
Draft control
Independent, electronic, manual/automatic PTO vs live, mechanical PTO.
Electronic 4X4
4 cylinders vs 3 cylinders
Way more 3 pt lift (amount escapes me now)
2 pedal design hst vs rocker style. There are also issues with the hst on the CK's, I had them and they split and replaced my hst.
Functional split breaks
Many more indicator lights on the dash (4X4, PTO, split breaks etc)
3pt lift control from the rear of the tractor (a crowd favorite)
Just bigger, stronger and heavier.
Horn
1 standard remote vs none standard. Additional remotes are $350 for either CK or DK or $500-$600 installed.
Probably a bunch more, but if I could get that package for $200, it wouldn't take me long to decide.
The Kubota is nice to. It is an older, non current model, but it would compare well to a DK 40 although I'd still take the DK40 anyday of the week. I do really like the replacement of the LXX30 series, the LXX40 series. The HST+ would be something I'd love, but you won't get that on the LXX30 series.